Potentiometric device



May 17, 1966 B. H. TlCE POTENTIOMETRIC DEVICE 4 Filed March 23, 1964 64 fZFIG 3 FIGZ INVENTOR.

BILLY H. 'TICE BYFULWIDER. PAT TON.

RIEBER. LEE & UTECHT ATTORNEYS 3,252,121 POTENTIOMETRIC DEVICE Billy H. Tice, 936 S. Citron St., Anaheim, Calif.

' Filed Mar. 23, 1964, Ser. No. 354,062

5 Claims. (Cl. 338-180) This invention relates to a potentiometric device, and more particularly to a precision potentiometriodevice characterized by high resolution through the utilization of a contactor or slider substantially completely encompassing the resistance means.

Potentiometers of the class to which the present invention is directed are operative to provide an output impedance which is variable in accordance With the relative positions of a slider and some from of resistance means. By way of example, one common form of prior art potentiometer utilizes a resistance element arranged in a helical pattern upon a coil form, and a slider element disposed in engagement with the resistance element so that upon application of an electrical potential adjacent the opposite ends of the resistance element theimpedance of the potentiometer may be varied bymoving the slider across adjacent turns of the resistance element. In some prior art potentiometers the slider is moved longitudinally or axially, without rotation, and in others a rotor mounting the slider is engaged with a helical track in the potentiometer housing for combined rotation and axial movement of the slider as the slider follows the helical path of the resistance element. I

In those devices in which the slider is moved in a purely axial or longitudinal direction, the resolution of the potentiometer is limited by the ratio of the resistance of each turn of the resistance element to the total resistance of the resistance element, providing an unsatisfactory arrangement in applications where extremely high resolution is required. Moreover,electrical noise is inherent in such an arrangement because of the transitional engagement of the slider with adjacentturns of the .extending shoe or the like'which precisely tracks and en- 'gages one turn of the electrical resistance element, following it along ,the helical path to achieve the desired high resolution. Obviously, such an arrangement is inherently limited to a resistance element in which the several turns thereof are generously spaced-apart or are constituted of. relatively large diameter wire to accommodate the body of the slider shoe, consequently limiting the capacity of the potentiometric device.

Other prior art potentiometric devices employ a slider guided in a helical path about the helically wound resistance element, and in which the slider utilizes a contact prong or finger disposed beneath a turn of the resistance element. The finger separates a portion or loop of the resistance element from. the coil form, and the loop of separated resistance element serves as -a guide track for the circumferential travel of the slider, about the coil form. Such an arrangement permits the use of a great plurality of turns of very fine resistance wire for the achievement of high resolution, but the requisite flexiblity of the Wire to accommodate the constant change in direction thereof during engagement by the traveling slider reduces the service life of such a potentiometric device considerably, and the delicacy of the slidable engagement between the slider and the wire is not conducive to shock and vibration resistance, rendering the arrangement unsuitable for space vehicles, for example.

Accordingly, it is an object of the present invention to provide a potentiometric device having an output voltage change which increases or decreases in imperceptible increments to produce high resolution, or what is popularly termed infinite resolution.

It is another object of the invention to provide a potentiometric device'of the aforementioned character adapted to provide a linear or non-linear output and characterized by low electrical noise and minimum distortion.

Another object of the invention is to provide a potentiometric device of the aforementioned character having resistance means supported to define a periphery of substantially uniform transverse dimensions, and having a slider which is longitudinally movable upon the resistance meansand arranged to substantially completely encompass the periphery of the resistance means for contact therewith at a great plurality of points. In one embodiment of the invention the resistance means is an electrically conductive Wire arranged in a helical pattern upon a cylinder coil form, and the slider is constituted by a length 0f coiled wire encircling the resistance element and joined together at its ends. The coils of the wire are resilient for biasing the circular slider against the resistance wire so that axial, slidable movement of the circular slider over the helical resistance element has the elfect of advancing the points of engagement therebetween along the helical pattern of the resistance element. The successive, newly established points of contact .are closely adjacent each other along the length of the helical resistance element, and provide a desirable, extremely high resolution.

A further object of the invention is the provision of a potentiometric device of the aforementioned character wherein the slider encompassing the resistance means is engaged by astructure which extends coextensive with the slider to support the slider and urge it into substantially continuous engagement with the resistance means, whereby the slider is maintained in positive contact with the resistance means during periods of exposure of the respect to the coil form during rotation of the slider about 7 the coil form. This arrangement affords a means for making fine adjustments in the axial position of the slider, and desirably enhances the resolution of the potentiometric device.

A further object of the invention is the provision of a potentiometric device of the aforementioned character wherein the coil form mounting the helical pattern of resistance wire is removable for substitution of a diiferent coil form to provide a helical pattern having a differently pitched helix angle to thereby provide, for example, a predetermined, non-linear voltage output. Such alteration of the output voltage characteristics can thus be made without any adjustment of the slider, the rotor,

.or the means embodying the guide helix. Only the coil form need be removed and replaced to provide apotentiometric device tailored for particular applications.

Other objects and features of the present invention will become apparent to those skilled in the art from the following specification and accompanying drawings wherein 3 are illustrated various forms of the invention, and in which:

FIG. 1 is a perspective view, primarily diagrammatic, of a potentiometric device according to the present invention;

FIG. 2 is a diagrammatic end elevation of another form of potentiometric device according to the present invention;

FIG. 3 is a longitudinal cross-sectional view of a potentiometric device wherein a circular slider is rotated within a guide helix to effect axial travel thereof over a cylindrical coil form; and

FIG. 4 is a view taken along the line 44 of FIG. 3.

Referring now to the drawings, and particularly to FIG. 1 thereof, there is illustrated a potentiometric device 10 which includes resistance means 12 suitably supported to define a periphery having substantially uniform transverse dimensions, the configuration of the periphery in FIG. 1 being cylindrical. The device 10 also includes a slider 14 which is axially or longitudinally movable upon the resistance means 12 and which substantially completely encompasses the periphery of a transverse section or annular segment of the cylindrical resistance means 12.

The slider 14 is preferably resilient so that it has an inherent bias tending to urged the slider 14 into contact with the resistance means 12 at a plurality of points about the periphery thereof, the points of contact for all practical purposes being continuous about the periphery to provide very high resolution.

In FIG. 2 another form of slider, designated by the numeral 16, is illustrated in association with a resistance means 18 having a square transverse cross-section, thereby showing that the present invention is not limited to circular or cylindrical configurations. The particular slider 16 is generally square in cross-section, but has its sides bowed inwardly for resilient engagement with the associated sides of the resistance means 18. For this purpose, the slider 16 is made of a resilient, electrically conductive wireadapted to be initially deformed inwardly so that upon subsequent disposition over the resistance means 18, the deformed or bowed sides of the slider 16 are biased against the sides of the resistance means 18 to effect good electrical contact therewith. 7

In either of the embodiments of FIGS. 1 and 2, the operation of the devices is similar. For example, in FIG. 1, axial or longitudinal movement of the slider 14 over the periphery'of the resistance means 12 is etfective to vary the resistance between anoutput terminal 20, connected to the slider 14, and each of a pair of input terminals 22 and 24 across Which the resistance means 12 is connected. Thus, When an electrical potential is applied adjacent the opposite ends of the resistance means 12 by means of the input terminals 22 and 24, movement of the slider 14 in an axial direction increases or decreases the voltage output of the devicelt).

The resistance means 12 generally takes the form of a conventional, helically wound resistance wire, but it may also be a ceramic body having a predetermined coefficient of resistance, or be other well known forms of resistance bodies or materials arranged in a form such that the slider 14 can move thereover. Further, the resistance may be constant throughout its length, or it may be made variable in accordance with some predetermined function, as desired. In the case of a resistance wire this can be accomplished, for example, by varying the pitch of the helix angle to yield a non-linear voltage output as the slider 14 moves from one extremity of the resistance means 12 to the other.

The nature and construction of the slider 14 is also subject to a number of modifications. Although preferably made of a coil of spring-like or resilient wire, it may be constituted of a ring or circle of wire or other electrically conductive material completely encompassing the resistance means 12. However constituted or constructed, slider 14 preferably is arranged to resiliently engage the periphery of the adjacent resistance means 12 for establishing good electrical contact therewith throughout its extent.

When the resistance means 12 is constituted by a wire which is wound in a helical pattern about a coil form or body, the potentiometric device 10 then comprises'the well-known multiturn potentiometer arrangement of the prior art, with the important difference, according to the present invention, that the arrangement is characterized by a high or infinite resolution because of the utilization of the encompassing engagement by the slider 14. That is, the axial travel of the slider 14, whether such travel is purely axial or the result of a traveling nut arrangement, does not merely provide a single, moving contact point traveling from the crest of one resistance turn to an adjacent resistance turn, but provides a great number of contact points progressively following the helical path of the wound resistance winding, thereby providing a desirably high resolution.

The showing in FIGS. 1 and 2 is diagrammatic to convey the broad scope of the present invention and the variety of forms which it may assume. A particular form of potentiometric device 26 is illustrated in detail in FIGS. 2 and 3 to illustrate an actual embodiment. The device 26 comprises an electrically conductive resistance element or Wire 28 wound over a cylindrical drum or coil form 30 in a helical pattern, the coil form 30 being fixed in position by securement to a housing 32 which is constituted by a cylindrical casing 34 whose opposite ends are closed by end bells or end members 36 and 38.

The coil form 30 is made of any suitable insulating material, and along the major portion of its length is spaced from the inner Wall of the cylindrical casing 34 to provide an annular space 40. In addition, the coil form 30 includes at one extremity a larger diameter end boss 42 which is carried within an annular groove in the adjacent extremity of the casing 34 to seat against an annular shoulder 44 defining the inner terminus of the annular groove. The end member 36 is forced against the outer extremity of the end boss 42 to seat it firmly against the shoulder'44 by a plurality of set screws, one of which is illustrated at 46, which are disposed through suitable openings in the casing 34 and into engagement with an annular groove 48 provided in the periphery of the end member 36. The depth of groove 48 diminishes in an inward direction so that as the set screws 46 are tightened into position the screws 46 urge the end members 1 36 inwardly.

A similar arrangement is provided at the opposite end of the casing 34, the end member 38 being provided with a peripheral groove 50 for receiving a plurality of set screws, one of which isillustrated at 52, to urge the end member 38 inwardly into tight engagement with the ad:

jacent extremity of the casing 34. In addition, the end member 38 is provided with an annular flange 54 which is adapted to be clamped by appropriate structure (not shown) for mounting the potentiometric device 26 in position for use with a larger piece of equipment.

The helical pattern of the resistance wire 28 is preferably characterized by a helix angle of substantially constant pitch to provide a substantially linear voltage output for the device 26, although it will be obvious that the helix angle may be altered in accordance with a predetermined pattern to provide a desired non-linear voltage output. Moreover, the resistance wire 28 is merely exemplary, as previously indicated, and could take the form of an electrically resistant ceramic coil form 30, or a' deposition of electrically resistant material upon the coil form 30.

For the purposes of applying an electrical potential to the opposite extremities of the resistance wire 28, a pair of electrically conductive pins 56 and '58 are secured Within suitable openings in the coil form 30 in electrical contact with the opposite extremities of the' resistance wire 28, and a pair of leads 60 and 62 are connected to the pins 56 and 58, respectively,-and led out of the housing 32 through suitable openings therefor and connected to external terminals, one of which is illustrated at 64.

With this arrangement, the housing 32, the coil form 30, and its associated resistance wire 28 are stationary. The movable portions of the potentiometric device 26 include a circular contactor or slider 66 which is supported by a circular support or rotor 68 which is made of electrical insulating material and arranged coextensive with the slider 66. Although the slider 66 maytake a variety of forms, such as a single wire disposed about the periphery of a transverse section of the cylindrical coil form 30,

encompassing approximately 360 degrees thereof, the

slider 66 is preferably constituted of an electrically conductive wire arranged in a coil which is disposed about the periphery of the coil form 30 and flattened at its outer portion to provide an apex for seating within an annular groove 70 provided in the circular rotor 68.

The rotor 68 has an internal diameter such that it normally tends to urge the slider 66 inwardly into resilient engagement with the resistance wire 28 to provide good electrical contact therewith about the complete periphery of the transverse section of the adjacent resistance wire 28.

Although the rotor 68 is generally circular, it includes diametrically disposed, radially outwardly extending arcuate guide portions 72 and 74, as best illustrated in FIG. 3, which are received within a helical groove provided in the interior .wall of the casing 34. The helical groove constitutes a guide helix 76 for guiding the rotor 68 in an axial direction during relative slidable movement between the guide helix 76 and the guide portions 72 and 74.

The guide portion 72 of the rotor 68 is slotted at 78 to accommodate a brush 80 coated with or made of a precious metal such as platinum. The brush 80 is secured to a pin 82 which is oriented in an axial direction and secured to the guide portion 72 of the rotor 68. The opposite extremity of the brush 80 is characterized by a pair of prongs which straddle sides of an axially extending conductor or support bar 84 made of electrically conductive material, the brush 80 being axially slidable relative to the bar 84 during axial movement of the rotor 68.v

One end of the bar 84 is disposed through a suitable opening provided in a cylindrical support member 86, which is made of insulating material and is rotatable upon and supported at one extremity by an electrically conductive brush ring 88 secured to the adjacent periphery of the coil form 30.

A brush 90, similar to the brush 80, is secured tothe end of the bar 84 with its prongs extending into slidable engagement with the brush ring 88 to provide an elec trical path from the slider 66, to the brush 80, thence to the bar 84, through the brush 90, and to the brush ring 88. An electrical lead 92 connects the brush ring 88 to a suitable exterior output terminal (not shown) which is mounted upon the outer periphery of the housing 32.

The opposite extremity of teh bar 84 is rigidly secured, as by a suitable adhesive, to the opposite extremity of the cylindrical support member 86 which, in turn, is rigidly secured, as by a suitable adhesive, to a circular yoke 96 which is secured to an axially extending shaft 98 by a transverse pin 100. The shaft 98 is rotatably supported by the inner races of a pair of roller bearings 102 and 104 located at the opposite extremities of the housing 32 in the end members 36 and 38, the bearing 104 being maintained in position by engagement between its inner race and the adjacent face of the yoke 96, and the bearing 102 being retained in position by a retainer ring 106 carried within a suitable annular slot in the shaft 98.

With this arrangement, rotation of the shaft 98 effects rotation of the cylindrical support member 86, carrying the bar 84 in a circumferentialpath about the shaft 98, the bar 84 extending within an axially extending opening 99 provided therefor in the support member 86.

-Rotation of the bar 84 carries the rotor 68 and the slider 66 with it, the slider 66 sliding around the resistance wire 28 upon the coil form 30. In addition, the rotation of the rotor 68 is translated into an axial movement thereof, by reason of its engagement with the guide helix 76, so that the slider 66 also moves axially relative to the coil form 30.-

Since the slider 66 substantially completely encompasses the periphery of a transverse section of the resistance wire 28, the slider 66 is in electrical contact with the resistance wire 28 at a great plurality of points about the periphery of the adjacent transverse section thereof. Accordingly, the potentiometric device 10 is characterized by extremely high resolution, and the undesirable skipping of contact from one turn of the wire 28 to the next adjacent turn is completely eliminated. Consequently, there is practically no electrical noise and the device 10 is capable of producing a linear voltage output. Moreover, constraint of the rotor 68 upon the slider 66 maintains the slider 66 in electrical contact with the electrical resistance wire 28 at all times, even during periods of extreme shock and vibration. In addition, it will be apparent that the coil form -may be removed andreplaced by a coil from having a different helix angle to provide a changing voltage output value to thereby render the voltage output non-linear, if desired. Thus, by the straight-forward expedient of providing a contactor or slider in substantially 360 degree engagement with a helically wound resistance wire, axial movement of the slider is eifective to change the voltage output of the potentiometric device in extremely small increments, the successive engagement between the slider and the resistance wire providing desirably high resolution as a consequence.

In view of the foregoing description it will be apparent that numerous other modifications and alternations may be made in the potentiometric devices herein disclosed without departing from the spirit and scope of the invention. For example, the shaft for rotating the slider could be fixed, and the housing of the device rotated if desired, and, as previously indicated, the coil form need not necessarily be cylindrical, but could assume a variety 'of shapes, depending upon the particular application. In this regard,.it will also be apparent that the resistance means 28 could be disposed upon the inner periphery of a cylindrical supporting drum or coil form, with the slider 66 disposed inside the cylindrical coil form in substantially continuous engagement throughout its extent with the resistance means 28, that is, throughout substantially 360 degrees of the inner circumference of the resistance means 28. The slider 66 in this'case would be supported by a circular or annular rotor, the rotor carryingltheslider 66 on the outer edge or periphery thereof. Thus, the slider 66 would be disposed in contact with the resistance means 28 throughout the periphery of the slider 66. Accordingly, it is to be understood that the scope of the invention is limited only by the scope of the appended claims.

I claim:

1. A potentiometric device comprising:

elongated resistance means supported to define a cylindrical periphery;

a slider movable over said resistance means, said slider substantially completely encompassing said resistance means in contact therewith at a plurality of points;

a rotor coextensive with and mounting said slider, and including a flange portion; 4

a housing enclosing said resistance means and said said rotor and including a helical track coextensive with said resistance means in coaxial and spaced relation thereto for slidably receiving said flange portion of said rotor, one of said flange portion and said housing being made of electrical insulating material to insulate said slider from the exterior surface of said housing;

means for effecting relative rotation between said housing and said rotor to move said flange portion of said rotor along said helical track to advance said slider over said resistance means, said means including an electrically conductive portion elect-ically coupled to said slider;

electrically conductive means coupled to said electrically conductive portion and extending externally of said housing; and

electrically conductive means coupled to opposite extremities of said resistance means and extending externally of said housing.

2. A wire wound potentiometric device comprising:

a housing;

an elongated cylindrical coil form fixed to and within said housing;

a resistance wire wound over said coil form in a helical pattern;

a slider sl-idable upon said resistance wire, said slider being spaced from the interior'surface of said housing and substantially completely encompassing said resistance wire in substantially complete contact along said slider; v

a rotor within said housing coextensive with and rnounting said slider to urge said slider into circumferential contact with said resistance wire, said rotor including a flange portion, said housing including a helical track slidably receiving said flange portion of said rotor, said track being coextensive with said resistance wire in coaxial and spaced relation therewith, one of said housing and said flange portion being made of electrical insulating material to insulate said slider from the exterior surface of said housing;

means for applying an electrical potential to said resistance wire adjacent the opposite ends thereof;

means for rotating said rotor to move said flange portion of said rotor along said helical tnack to move said slider over said resistance wire, said means including an electrically conductive portion electrically coupled to said slider; and

electrically conductive means coupled to said electrically conductive portion and extending externally of said housing.

3. A potentiometric device, comprising:

a housing;

an elongated body having a substantially uniform transverse cross section along the longitudinal axis thereof, said body being fixed Within said housing against both rotational and axial movement relative to said housing;

resistance means carried upon the periphery of said body;

a positioning shaft rotatably carried by said housing and extending through the interior thereof parallel to said body; p

a slider engaged upon and movable over said resistance means and substantially completely encompassing the periphery of a transverse section thereof whereby said slider is in contact with said periphery at a plurality of points, said slider being resilient and biased against said resistance means to provide good electrical contact therewith;

a slider support mounting said slider and engaged upon the interior surface of said housing, one of said housing and said slider support being made of electrical insulating material'to insulate said slider from the exterior surface of said housing;

means coupling said positioning shaft and said slider support and operative in cooperation with said housing to advance said slider support in a longitudinal direction upon rotation of said shaft thereby to carry said slider over said resistance means, said coupling means including an. electrically conductive portion electrically coupled to said slider;

electrically conductive means coupled to said electrically conductive portion and extending externally of said housing;

and electrically conductive means coupled to opposite extremities of said resistance means and extending externally of said housing. 7

4. A potentiometric device according to claim 3 wherein said resistance means is constituted of a resistance element supported and arranged upon said body in a helical pattern.

5. A potentiometric device according to claim 3 wherein said slider is constituted of an electrically conductive wire of helical configuration disposed about the periphery of said body. a v

References Cited by the Examiner UNITED STATES PATENTS RICHARD M. WOOD, Primary Examiner.

ANTHONY BARTIS, Examiner. 

1. A POTENTIOMETRIC DEVICE COMPRISING: ELONGATED RESISTANCE MEANS SUPPORTED TO DEFINE A CYLINDRICAL PERIPHERY; A SLIDER MOVABLE OVER SAID RESISTANCE MEANS, SAID SLIDER SUBSTANTIALLY COMPLETELY ENCOMPASSING SAID RESISTANCE MEANS IN CONTACT THEREWITH AT A PLURALITY OF POINTS; A ROTOR COEXTENSIVE WITH AND MOUNTING SAID SLIDER, AND INCLUDING A FLANGE PORTION; A HOUSING ENCLOSING SAID RESISTANCE MEANS AND SAID SAID ROTOR AND INCLUDING A HELICAL TRACK COEXTENSIVE WITH SAID RESISTANCE MEANS IN COAXIAL AND SPACED RELATION THERETO FOR SLIDABLY RECEIVING SAID FLANGE PORTION OF SAID ROTOR, ONE OF SAID FLANGE PORTION AND AID HOUSING BEING MADE OF ELECTRICAL INSULTING MATERIAL TO INSULATE SAID SLIDER FROM THE EXTERIOR SURFACE OF SAID HOUSING; MEANS FOR EFFECTING RELATIVE ROTATION BETWEEN SAID HOUSING AND SAID ROTOR TO MOVE SAID FLANGE PORTION OF SAID ROTOR ALONG SAID HELICAL TRACK TO ADVANCE SAID SLIDER OVER SAID RESISTANCE MEANS, SAID MEANS INCLUDING AN ELECTRICALLY CONDUCTIVE PORTION ELECTRICALLY COUPLED TO SAID SLIDER; ELECTRICALLY CONDUCTIVE MEANS COUPLED TO SAID ELECTRICALLY CONDUCTIVE PORTION AND EXTENDING EXTERNALLY OF SAID HOUSING; AND ELECTRICALLY CONDUCTIVE MEANS COUPLED TO OPPOSITE EXTREMITIES OF SAID RESISTANCE MEANS AND EXTENDING EXTERNALLY OF SAID HOUSING. 